Later studies found that the citrate anticoagulation used for platelet aggregation studies resulted in an overestimation of the inhibition by eptifibatide of platelet aggregation. Thus, it is unclear whether there is a differential effect of eptifibatide on the bleeding time.
Studies of C-eptifibatide administered as a single 135 g/kg IV bolus revealed mean peak plasma concentrations of 879 ± 251 ng/mL at 5 min, a mean distribution half-life of 5 ± 2.5 min, and a mean terminal elimination half-life of 1.1 ± 0.17 h. Of the approximately 73% of administered radioactivity recovered in 72 h, renal clearance accounted for 98% of the total recovered radioactivity, and for approximately 40% of total body clearance. Unmodified eptifibatide, deamidated eptifibatide, and more polar metabolites were all found in the urine, but only trace amounts of radioactivity were found in the breath and feces.
Since renal clearance is an important component of eptifibatide catabolism, patients with renal impairment can have prolonged inhibition of platelet function after receiving eptifibatide. This is of particular theoretical concern because patients with end-stage renal failure have platelet dysfunction Sildenafil Citrate Australia. The proper dose of eptifibatide in patients with modest-to-moderate renal insufficiency (creatinine level, 2 to 4 mg/dL) is uncertain. In the Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial, patients with creatinine clearances of < 60 mL/min had increased major and minor bleeding rates compared to those patients with creatinine clearances of > 60 mL/min, and eptifibatide treatment increased both major and minor bleeding in both groups of patients.
Since the steady-state level of eptifibatide is approximately 1,900 ng/mL when using an infusion rate of 2 g/kg/min, the ratio of eptifibatide molecules to GPIIb/ IIIa molecules is > 50:1. Thus, platelet transfusions may not be able to reverse the effects of the drug, although in vitro data raise some hope in this regard. Treatment with eptifibatide prolongs the activated clotting time of patients who have received heparin, suggesting an inhibitory effect on thrombin generation.
In 21 patients undergoing elective PTCA or directional coronary atherectomy who were treated with aspirin, heparin (10,000 U bolus plus additional doses to maintain an activated clotting time of 300 to 350 s), and a bolus dose of 90 g/kg eptifibatide followed by infusion at a rate of 1 g/kg/min for 4 or 12 h, platelet aggregation was measured before infusion, 1 h after the bolus administration, at the end of the infusion, and 4 h after the end of the infusion. The extent of platelet aggregation in response to 20 mol/L ADP administration decreased from approximately 80% before eptifibatide administration to approximately 15% at both 1 h after the administration of the bolus dose and at the end of the infusion.
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